Magnetoelectric Coefficient Research Articles

Modifying the Magnetic and Electronic Properties of Monolayer 2H‐VS 2 via Ferroelectric Substrate with Different Surface Terminations

A promising strategy to tailor the magnetic and electronic properties of 2D van der Waals magnets is to integrate them with a ferroelectric (FE) substrate. Herein, the FE substrate effect of BiFeO3(0001) with different surface terminations is explored using density functional theory calculations for the ferromagnetic 2H-VS2 monolayer. It is observed that depending on the polarization direction and surface termination of the BiFeO3(0001) FE substrate, the 2H-VS2/BiFeO3(0001) interface exhibits a substantially varied charge transfer behavior. The magnetic and electronic properties of the monolayer 2H-VS2 are significantly modulated by the interface charge transfer. Furthermore, in the 2H-VS2/BiFeO3(0001) heterostructures, large interface magnetoelectric coupling coefficients are predicted. The in-plane magnetic and electronic properties of monolayer 2H-VS2 can be effectively tuned by the out-of-plane FE polarization, paving the way for a novel class of spintronic devices based on the 2H-VS2/BiFeO3(0001) hybrid system.

Giant electric field–controlled magnetism in Bi0.86Sm0.14FeO3 multiferroic ceramics with Pna21 symmetry

AbstractIn the present work, Bi0.86Sm0.14FeO3 ceramics with near Pna21 single‐phase structure were obtained by a repeated longtime sintering process, and the dielectric, ferroelectric, and magnetic characteristics were determined together with the magnetoelectric coupling coefficient. The evolution of Pna21 symmetry was revealed by transmission electron microscope analysis, and the ferroelectric transition from Pbnm to Pna21 was determined by differential scanning calorimetry analysis together with the dielectric characterization, and the Curie temperature was determined as 195°C. The saturated polarization–electric field (P–E) hysteresis loop was obtained with Pr = 12.2 μC cm−2, and the unlocking of ferromagnetism was confirmed by the apparent magnetization–magnetic field (M–H) hysteresis loop with Mr = 77.4 emu mol−1. The giant electric field–controlled magnetism was due to the Pna21/R3c field–induced transition, which was confirmed by both structure analysis and theoretical calculation, and the change of remanent magnetization under an electric field was achieved up to 44.8 emu mol−1 (57.9%), which was much bigger than that of rare‐earth (RE)‐substituted BiFeO3 ceramics without optimizing Pna21 phase fraction. The present results might significantly deepen the physical understanding of Pna21 phase and subsequently provide new hints on further enhancing electric field–controlled magnetism in RE‐substituted BiFeO3 multiferroic ceramics.

Strain Modulation of Perpendicular Magnetic Anisotropy in Wrinkle-Patterned (Co/Pt)5/BaTiO3 Magnetoelectric Heterostructures.

The rapid development of spintronics requires the devices to be flexible, to be used in wearable electronics, and controllable, to be used with magnetoelectric (ME) structures. However, the clamping effect inevitably leads to a decreased ME effect on the rigid substrate, and it remains challenging to directly prepare high-quality ferroelectric (FE) membranes on the widely used flexible substrate such as MICA or polyimide (PI). Here, periodic wrinkle-patterned flexible (Co/Pt)5/BaTiO3 (BTO) perpendicular magnetic anisotropy (PMA) heterostructures were prepared using the water-soluble method. The high-quality single-crystal BTO membrane ensures that intricate wrinkles do not fracture and a high ME coefficient is achievable. The transferred sample that is released from the clamping effect shows an enhanced ME effect in both in-plane and out-of-plane directions, with the ME coefficient reaching up to 68 Oe °C-1. The ferromagnetic resonance (FMR) field of the flexible sample can be tuned by tensile strain up to 272 Oe. The finely controlled wrinkle shows periodic strain variations at peak and valley regions that switch the PMA magnetic domain motion as an effective control method. The proposed ultraflexible wrinkle sample shows great potential for combining multiple magnetization tuning approaches, allowing it to potentially serve as a tunable high-density 3D storage prototype.

A magnetoelectric nanocomposite based on two dimensional Cr2O3 and CoFe2O4

Nanocomposites consisting of 2 dimensional (2D) amorphous Cr2O3-CoFe2O4 and crystalline 2D Cr2O3-CoFe2O4 were prepared and the room temperature magnetoelectric coupling was studied. This study also investigated the effect of crystalline 2D Cr2O3 on the exchange bias induced magnetoelectric coupling in the composites. Evidence for the exchange bias in the composites is obtained from field cooling - zero field cooling (FC-ZFC) measurements. The 2D crystalline Cr2O3 composite exhibits high magnetoelectric coupling coefficient at room temperature when compared to bulk composite for the corresponding Cr2O3. These composites augurs well for applications especially for energy harvesting and spintronics.

Sensitive electric field control of first-order phase transition in epitaxial multiferroic heterostructures

Strongly correlated electron materials that exhibit rich phase transition and multiple phase separation have shown many fascinating properties. Using these properties in the electronic device will require the ability to control their phase transition and phase separation behaviours. In this work, we report a sensitive electric field control of first-order phase transition in epitaxial (011)-Nd0.5Sr0.5MnO3/0.71Pb(Mg1/3Nb2/3)O3–0.29PbTiO3 (PMN-PT) heterostructure. The pristine film shows phase separation character with the penetration of the ferromagnetic metallic phase into the charge and orbital ordered antiferromagnetic insulating phase, and this was revealed by the XMCD and XLD investigation. The (011)-oriented PMN-PT piezoelectric single crystal adopted can exert anisotropic in-plane tensile strains on the epitaxial Nd0.5Sr0.5MnO3 film when applying the electric field. The coaction of the electric field-induced strain and polarization effects of the PMN-PT piezoelectrics enable the efficient manipulation of orbital ordering and the coupled electronic and magnetic phase transitions. Accordingly, a small +1.6 kV cm−1 electric field can recover the first-order metal-insulator transition which was inhibited in the pristine heterostructure, increase the transition temperature by 56 K and the maximum resistance change reaches 7033%. Furthermore, the electric field demonstrated non-volatile control of magnetization, and the magnetoelectric coefficient reaches 1.89 × 10−7 s m−1 at 200 K. This work indicates that choosing the piezoelectric substrate with appropriate electric-field-induced strain opens a route to designing functional electronic devices where the tunable macroscopic properties derive from strongly interacting degrees of freedom present in the manganite.

BaTiO3/(Co0.8Ni0.1Mn0.1Fe1.9Ce0.1O4)x composites: Analysis of the effect of Co0.8Ni0.1Mn0.1Fe1.9Ce0.1O4 doping at different concentrations on the structural, morphological, optical, magnetic, and magnetoelectric coupling properties of BaTiO3

In the present study, composite samples of BaTiO3/(Co0.8Ni0.1Mn0.1Fe1.9Ce0.1O4)x (noted as BTO/(CNMFCO)x) were prepared and their structural, morphological, optical, magnetic, and magnetoelectric coupling properties were investigated. Firstly, the BaTiO3 and spinel ferrite CNMFCO phases were prepared separately through the sol-gel auto-combustion route, then, the composite samples BTO/(CNMFCO)x were made via the solid-state reaction method. The structural, morphological, optical, magnetic, and magnetoelectric coupling properties were examined using X-rays diffraction (XRD), Fourier transform-infrared spectroscopy (FTIR), scanning electron microscope (SEM) coupled with EDX spectrometer, UV–visible diffuse reflectance spectrophotometer (UV–vis DRS), vibrating sample magnetometer (VSM) techniques, and lock-in amplifier, respectively. The successful preparation of biphasic samples was confirmed by XRD and SEM studies. From SEM images, a compact structure with good density was observed. The mean size of BTO grains decreases with increasing the concentration of the magnetic phase. The optical properties have been explored in the UV–visible light range. The extracted band gap energy (Eg) values showed a reduction with the rising of the magnetic phase content. The analysis of magnetization measurements revealed the magnetic character of different composites. It is found that the saturation (Ms) and remanent (Mr) magnetizations are increasing with the rise in the concentration of the magnetic CNMFCO phase (x %). High magnetoelectric voltage coefficients (αME) were attained for different composites with the highest αME value of about 22.8 mV/cm.Oe reached in composite with x content of 20%. The high ME coupling in these composites makes these composites promising candidates to be used in multifunctional devices.

Large magnetoelectric effect in BaFe12O19-(Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 particulate composite

Multiferroic composites with a large magnetoelectric response are gaining attractive interests for the design of magnetoelectric (ME) functional devices. In this work, the particulate ME composites (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3–xBaFe12O19 (x=0, 0.1, 0.2, 0.3, 0.4 and 1) were prepared, and their structural, dielectric, magnetic, ferroelectric, piezoelectric properties and magnetoelectric coupling were systematically investigated. The composites consisted of only two chemically separated phases with well-bonded interface. Dielectric and impedance analyses indicated the co-contribution of grain and grain boundary to polarization. Well-saturated ferroelectric and magnetic hysteresis loops demonstrated multiferroic nature. ME response was investigated elaborately by employing magnetically induced polarization, together with measuring ME voltage coefficient and magnetodielectric value. Specifically, a large ME coefficient of 26.78 ​mV/cm·Oe was achieved for x=0.3, which is higher than that in single-phase BaFe12O19 and its coupled composites.

Interface engineering in ferroelectrics: From films to bulks

As an important branch of functional materials, ferroic materials, especially ferroelectrics have attracted increasing attention in decades. Because of the rising demand in industry, performances on single-phase-based ferroelectric materials seems to meet the bottleneck, studies on composites are becoming urgent now. Motivated by this, structure designing of composite materials was considered as a key factor for pursing better properties, yielding fruitful research work. Among those work, interfacial parts between different phases was always reported to play significant roles in such composite ferroelectrics, and the authors summed them up as the strategy of INTERFACE ENGINEERING. Being different from traditional reviews, which mostly introduce materials with certain system or function, this one focuses more on the utilizing of interfaces in different states of ferroelectrics such as: Tuning magnetoelectric coupling coefficient by terminated layer in epitaxial thin films; broadening Curie Temperature range by inducing interfacial stain; enhancing dielectric tunability by forming topological structures; increasing electrical breakdown strength introducing artificial interfaces, etc . Besides, deeper mechanisms of such performance optimizations were also digged out and explained, hoping to offer new ideas for exploiting the next-generation electronic materials and devices.

Finite element analysis of the magnetoelectric effect on hybrid magnetoelectric composites

The multi-component hybrid magnetoelectric (ME) composites obtained by using high molecular polymer as the first component and ferromagnetic or ferroelectric material as the second component by hierarchical compounding has the advantages of light weight, easy processing and flexibility. It has the characteristics of good performance and can also realize the conversion between magnetic energy and electric energy, which has potential applications in the fields of bionic robots and medical non-invasive detection. In this study, the finite element method is used to study its ME effect. Considering the distribution characteristics of the component materials and their nonlinear constitutive equations, as well as the dynamic equation and the corresponding mechanical and electrical boundary conditions, a finite element model of the ME effect of the ME composites is established. The distribution of elastic field, magnetic field and electric field of the hybrid ME composites were studied, and the influence of microstructural distribution characteristics, geometric parameters, external magnetic field, temperature and other factors on its magnetoelectric coefficient was analyzed. The calculated results can provide the theoretical guidance for the optimal design of high-performance magnetoelectric devices and render better support for the technological development in the field of magnetoelectricity.

Magnetoelectric effects in shear-mode magnetostrictive/piezoelectric composite with a Z-type structure

A shear-mode trilayer magnetoelectric (ME) laminate heterostructure comprising giant magnetostrictive materials (GMMs) and a piezoelectric plate has been prepared in this study. Based on theoretical calculations, the piezoelectric plate with a Z-type structure is subjected to more stress from the magnetostrictive material, which indicates that the stress transfer capacity of the Z-type structure is higher than that of the traditional S-type structure. Experimental research demonstrated that the magnetoelectric coupling coefficient of the Z-type structure is 1.5 times higher than that of the S-type structure. Its ME coupling coefficient exceeded frequency response range was 8 times that of the S-type structure, and vibration displacement was ∼ 2.2 times that of the S-type structure. Finite element simulations have also been performed to calculate the voltage distribution of the shear-mode trilayer ME laminate heterostructure. Since such broadband ME structures are capable of magnetic field detection, this research elucidates the applicability of ME laminate heterostructures for transducing, sensing, and energy harvesting.

Anisotropic magnetoelectric effect in lead zirconate titanate and magnetostrictive fiber composite structures

Objectives. The development of composite structures in which a strongly anisotropic magnetoelectric (ME) effect is observed is relevant for the creation of sensors that are sensitive to the direction of the magnetic field. Such an ME effect can arise due to the anisotropy of both the magnetic and the piezoelectric layers. In this work, a new anisotropic material named as a magnetostrictive fiber composite (MFC), comprising a set of nickel wires placed closely parallel to each other in one layer and immersed in a polymer matrix, is manufactured and studied. The study aimed to investigate the linear ME effect in a structure comprising of a new magnetic material, MFC, and lead zirconate titanate (PZT-19).Methods. The magnetostriction for the MFC structure was measured using the strain-gauge method; the ME effect was determined by low-frequency magnetic field modulation.Results. Structures with nickel wire diameters of 100, 150, and 200 μm were fabricated. The MFC magnetostriction field dependences were determined along with the frequency-, field-, and amplitude dependences of the ME voltage in the case of linear ME effect. Measurements were carried out at various values of the angle between the direction of the magnetic field and the wires. All samples demonstrated strong anisotropy with respect to the direction of the magnetic field. When the magnetic field orientation changes from parallel to perpendicular with respect to the nickel wire axes, the ME voltage decreases from its maximum value to zero.Conclusions. The largest ME coefficient 1.71 V/(Oe · cm) was obtained for a structure made of MFC with a wire diameter of 150 μm. With increasing wire diameter, the resonance frequency increases from 3.5 to 6.5 kHz. The magnetostriction of the MFC is comparable in magnitude to that of a nickel plate having the same thickness.

Magnetoelectric effects in stripe- and periodic heterostructures based on nickel–lead zirconate titanate bilayers

Objectives. A topical task in the design of magnetoelectric (ME) devices based on composite ferromagnetic– piezoelectric heterostructures involves reducing their dimensions to increase their operating frequencies and optimize their integration in modern electronics. The study set out to investigate the influence of in-plane dimensions on the characteristics of ME effects in stripe and periodic nickel–lead zirconate titanate heterostructures manufactured via electrolytic deposition.Methods. Lead zirconate titanate disks with Ag-electrodes were used for manufacturing the ME heterostructures; Ni was deposited on one Ag-electrode only.Results. While a reduction in stripe size leads to an increase in the frequency of the resonant ME effect, it is followed by a decrease in ME conversion efficiency. The ME coefficient for the periodic heterostructures is about ~1 V/(Oe·cm). By increasing the angle between the magnetic field H and the Ni-stripe axis from 0° to 90°, a 2.5-fold increase in the optimal field Hm and a 4-fold drop in the maximum amplitude of ME voltage umax(Hm) was achieved.Conclusions. In periodic heterostructures, the frequency of the resonant ME effect is determined by the substrate’s size, while ME conversion efficiency depends on the width of the Ni stripes and the distance between them. The observed anisotropy of the ME effects in the investigated heterostructures is explained in terms of demagnetization effects. In the future, the anisotropic ME effect in the periodic heterostructures could be used to develop magnetic field sensors that are sensitive to field orientation.

Synthesis of x[La0.67Sr0.33MnO3] – (1-x)[0.5Ba0.7Ca0.3TiO3-0.5BaZr0.2Ti0.8O3] multiferroic composite with its dielectric, magnetodielectric, magnetic and electrical conductivity studies

The present paper studies the synthesis and characterization of x[La0.67Sr0.33MnO3] – (1-x)[0.5Ba0.7Ca0.3TiO3-0.5BaZr0.2Ti0.8O3] multiferroic composite for x = 0.1 and 0.175. Parent materials of ferroelectrics Ba0.7Ca0.3TiO3 (BCT) and BaZr0.2Ti0.8O3 (BZT) and ferrite La0.67Sr0.33MnO3 (LSMO) have been prepared via hydroxide co-precipitation method while its composite x[LSMO] – (1-x)[0.5 BCT -0.5 BZT] was synthesized by ceramic route. The presence of ferroelectric and ferrite phases were confirmed by structural studies of composites. Microstructure shows the dense and closely packed LSMO particles over BCT-BZT ferroelectric phase. The dielectric properties of composites were studied in frequency range of 1KHz-1MHz and from room temperature to 500OC. P-E hysteresis loops of composites shows noticeable values of saturation polarization (Ps) and remnant polarization (Pr). Significant value of magnetoelectric (ME) coupling coefficient (α) of 2.15mV/cmOe was observed for the composite 0.175LSMO – 0.825(0.5BCT-0.5BZT) at 1 KHz frequency. Magnetodielectric (MD) properties of the composites were investigated by measuring the magnetocapacitance up to 1 T magnetic field. MD effect can be explained on the basis of contribution of dielectric constant due to interfacial polarization which depends on magnetic field and changes due to induced stress. Frequency dependent ac conductivity was confirmed by Jonscher's Universal Power law. Temperature dependent dc conductivity of the materials shows the Arrhenius behavior. As the ferrite content of LSMO increases in the composite saturation magnetization increases which can be studied by the hysteresis plot.

Strain‐mediated electrical and optical properties of novel lead‐free CuFe2O4–KNbO3 nanocomposite solid solutions: A combined experimental and Density Functional Theory studies

This article summarizes the strain-mediated electrical and optical properties of novel lead-free xCuFe2 O4 (1-x) KNbO3 (x= 0.2, 0.3, and 0.4) multiferroic nanocomposite through a solid state route. X-ray diffraction analysis divulges the influence of interfacial strain in the KNbO3 -CuFe2 O4 matrix and shows the coexistence of orthorhombic and cubic spinel phases, respectively. Morphological analysis reveals that the average particle size of 0.3CuFe2 O4 -0.7KNbO3 is 25 nm which is smaller than the other two nanocomposites. The UV-visible absorption studies and Raman spectroscopy of 0.3CuFe2 O4 -0.7KNbO3 nanocomposite present the high energy bandgap and electro coupling of KNbO3 and CuFe2 O4 phases. The DFT theoretical bandgap behaviors of all the three nanocomposites synchronize with the experimental bandgap results. Dielectric, ferroelectric and magnetoelectric behaviors are also improved in 0.3CuFe2 O4 -0.7KNbO3 nanocomposite as compared to pristine KNbO3 and the other two nanocomposites. HIGHLIGHTS: This article summarizes the strain-mediated electrical and optical properties of novel lead-free xCuFe2 O4 -(1-x) KNbO3 (x=0.2, 0.3, and 0.4) multiferroic nanocomposite through a solid state route. X-ray diffraction analysis divulges the influence of interfacial strain in the KNbO3 -CuFe2 O4 matrix and shows the coexistence of orthorhombic and cubic spinel phases, respectively. The 0.3CuFe2 O4 -0.7 KNbO3 nanocomposite shows a remarkable increase in the optical bandgap, remnant polarization, dielectric permittivity, and magnetoelectric coefficient compared to the other two nanocomposites. DFT calculations on KNbO3 -CuFe2 O4 matrix reveal the impact of diffusion between two phases and support the bandgap experimental results.

Multiferroic and energy harvesting characteristics of P(VDF-TrFE)-CuFe2O4 flexible films

Ferroelectric polymer-based multiferroics are very promising candidates for a wide variety of applications. To realize such a composite material with remarkable multiferroic behavior, we have developed CuFe 2 O 4 nanoparticles loaded poly (vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) films by a solvent casting approach. Different weight percentages (2, 4, 8 and 16) of CuFe 2 O 4 nanoparticles were achieved in the P(VDF-TrFE) matrix. Remarkable improvement in the multiferroic behavior has been observed with the addition of the magnetic nanoparticle. Through this approach, by adjusting the filler content we could vary the magnetoelectric coupling coefficient from 6.12 to 26.31 mVcm −1 Oe −1 . The piezoelectric energy harvesting performances of the prepared multiferroic materials were also studied. The energy harvesting devices based on the developed materials were produced output voltages between 3 and −3 V during repeated pressure imparting. • CuFe 2 O 4 nanoparticles loaded P(VDF-TrFE) films were developed by a solvent casting approach. • Dielectric, magnetic and magnetoelectric properties of the composites were enhanced with CuFe 2 O 4 nanoparticles loading. • The highest ME coefficient of 26.31 mVcm −1 Oe −1 was noticed for the composite film with 16 wt% of CuFe 2 O 4 nanoparticles. • Developed PEHDs produced output voltages between 3 and −3 V during repeated pressure imparting.

A Low-Frequency MEMS Magnetoelectric Antenna Based on Mechanical Resonance.

Antenna miniaturization technology has been a challenging problem in the field of antenna design. The demand for antenna miniaturization is even stronger because of the larger size of the antenna in the low-frequency band. In this paper, we consider MEMS magnetoelectric antennas based on mechanical resonance, which sense the magnetic fields of electromagnetic waves through the magnetoelectric (ME) effect at their mechanical resonance frequencies, giving a voltage output. A 70 μm diameter cantilever disk with SiO2/Cr/Au/AlN/Cr/Au/FeGaB stacked layers is prepared on a 300 μm silicon wafer using the five-masks micromachining process. The MEMS magnetoelectric antenna showed a giant ME coefficient is 2.928 kV/cm/Oe in mechanical resonance at 224.1 kHz. In addition, we demonstrate the ability of this MEMS magnetoelectric antenna to receive low-frequency signals. This MEMS magnetoelectric antenna can provide new ideas for miniaturization of low-frequency wireless communication systems. Meanwhile, it has the potential to detect weak electromagnetic field signals.

Robust ferroelectric-gating-dependent electronic and magnetic properties in a 1T-VSe2/BiAlO3(0001) multiferroic heterostructure

The modulation of magnetism and related electronic properties is highly desirable for advanced nanoscale electronic and spintronic applications, but volatility in electron spin manipulation is a major challenge that requires urgent attention. Here, we use density functional theory (DFT) calculations to show that the electronic and magnetic properties of a ferromagnetic [half-]metallic 1T-VSe2 monolayer can be effectively modulated via ferroelectric BiAlO3(0001) gating. In particular, the carry type in the 1T-VSe2 overlayer can be switched from being n-type to p-type or n+ -type through the reversal of the ferroelectric polarization. The magnetocrystalline anisotropy of the 1T-VSe2 monolayer can also be changed from easy-plane to easy-axis. In addition, the band offset, magnetic moments, exchange interaction, and Curie temperature (Tc) of the 1T-VSe2 overlayer show significant dependence on the electric polarization direction, with the calculated surface magnetoelectric coupling coefficients (αS) reaching 10−10 G cm [2]/V. This demonstration of robust ferroelectric-gating-dependent magnetism and related electronic properties holds great promise for the innovative design and implementation of next-generation nanoscale non-volatile ultra-low power devices.

Enhancing Converse Magnetoelectric Coupling Through Strain Engineering in Artificial Multiferroic Heterostructures.

Magnetoelectric materials present a unique opportunity for electric field-controlled magnetism. Even though strain-mediated multiferroic heterostructures have shown unprecedented increase in magnetoelectric coupling compared to single-phase materials, further improvements must be made before ultra-low power memory, logic, magnetic sensors, and wide spectrum antennas can be realized. This work presents how magnetoelectric coupling can be enhanced by simultaneously exploiting multiple strain engineering approaches in heterostructures composed of Fe0.5Co0.5/Ag multilayers on (011) Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 piezoelectric crystals. When grown and measured under strain, these heterostructures exhibit an effective converse magnetoelectric coefficient in the order of 10-5 s m-1: the highest directly measured, non-resonant value to-date. This response occurred at room temperature and at low electric fields (<2 kV cm-1). This large effect is enabled by magnetization reorientation caused by changing the magnetic anisotropy with strain from the substrate and the use of multilayered magnetic materials to minimize the internal stress from deposition. Additionally, the coercive field dependence of the magnetoelectric response under strain suggests contributions from domain-mediated magnetization switching modified by voltage-induced magnetoelastic anisotropy. This work highlights how multicomponent strain engineering enables enhanced magnetoelectric coupling in heterostructures and provides an approach to realize energy-efficient magnetoelectric applications.

Self-biased characteristics of NZCF/BCZT layered magnetoelectric composites: A novel coupling paradigm in magnetoelectricity

Here, we investigate room temperature magnetoelectric (ME) behavior of ferroelectric Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) and ferrimagnetic Ni0.75Zn0.20Co0.05Fe2O4 (NZCF) layered composites. The ferroelectric ceramics (thickness, t, ∼0.6, 0.8, and 1.0 mm) are stacked at magnetic specimen of fixed t ∼ 1 mm, coupled with conducting silver epoxy. The phase formation, surface morphology, dielectric, magnetic, magnetoelectric and magnetodielectric characteristics of bilayer composites have been studied in the present work. The maximum value of magnetoelectric (ME) coupling coefficient (αME) is found to be 70, 90, and 110 mVcm−1Oe−1 for composite having ferroelectric layer thickness t ∼ 1, 0.8, and 0.6 mm, respectively. More importantly, αME(H→0) remains finite for composite (t ∼ 0.8, and 0.6 mm) in zero magnetic field, which is a clear evidence of self-biasing phenomenon in NZCF/BCZT layered composite. For closer insight about underlying mechanism, we estimate magnetodielectric (MD) coefficient for the layered composite. The MD coefficient is found to be significantly high ∼6.32% for the thickness 0.6 mm. MD% vs magnetic field, H, curves exhibit steeper field dependence in low field region and for H≥2kOe MD possess saturation characteristics. The high saturation characteristics suggest that the magnetoelectricity in layered composite is driven by magnetostriction mechanism and causes robust ME coupling. Further, we obtain electrical signal ∼143 mV with the Hdc ∼250 Oe, as a consequence of interplaying nature of magneto(striction)- piezo(electricity). Such a sizeable response will improve the underlying intimacy between technology and practical application. The study reveals that the pellet based layered composites may be a proven strategy for the realization of self-biased ME devices.

In silico assessment of electrophysiological neuronal recordings mediated by magnetoelectric nanoparticles

Magnetoelectric materials hold untapped potential to revolutionize biomedical technologies. Sensing of biophysical processes in the brain is a particularly attractive application, with the prospect of using magnetoelectric nanoparticles (MENPs) as injectable agents for rapid brain-wide modulation and recording. Recent studies have demonstrated wireless brain stimulation in vivo using MENPs synthesized from cobalt ferrite (CFO) cores coated with piezoelectric barium titanate (BTO) shells. CFO–BTO core–shell MENPs have a relatively high magnetoelectric coefficient and have been proposed for direct magnetic particle imaging (MPI) of brain electrophysiology. However, the feasibility of acquiring such readouts has not been demonstrated or methodically quantified. Here we present the results of implementing a strain-based finite element magnetoelectric model of CFO–BTO core–shell MENPs and apply the model to quantify magnetization in response to neural electric fields. We use the model to determine optimal MENPs-mediated electrophysiological readouts both at the single neuron level and for MENPs diffusing in bulk neural tissue for in vivo scenarios. Our results lay the groundwork for MENP recording of electrophysiological signals and provide a broad analytical infrastructure to validate MENPs for biomedical applications.